Myofibroblast morphology: extension length and roundness. (A) Representative confocal images of single isolated human cardiac myofibroblasts embedded into a thin collagen nylon-based gel. Following treatments (control, TGFβ1, TGFβ1 + LMW-FGF-2), cells were stained for F-actin (phalloidin; green) while adjacent collagen matrix was visualized using confocal reflectance (red). (B) Cell extension length was measured from the cell centroid to the tip of a given cell extension. TGFβ1 increased mean cell extension length while LMW-FGF-2 restored levels close to baseline. Bars represent mean ± SD; *p < 0.05. (C) Roundness, a dimensionless shape factor, was quantified for each treatment group. Values closer to 1.0 represent round phenotypes while decreasing values <1.0 are representative of a star-shaped phenotype (activated). TGFβ1 treatment favored a more stellate-cell shape while LMW-FGF-2 showed morphology consistent with non-activated cells. Bars represent mean ± SD; *p < 0.05. Scale bar = 20 μm.